Higher Rydberg states of NO trapped in rare gas matrixes were studied by inducing Rydberg-Rydberg transitions from the lowest A2S+ (3ss) Rydberg state and detecting its fluorescence depletion. This technique unravels Rydberg states, which cannot be accessed by ground state absorption. However, no clear cut Rydberg series show up. The data show a compression of the n-(n + 1) splittings between Rydberg states, and of the ll splittings. The results are rationalized in terms of the quantum defect model and the lack of extended Rydberg series is due to the compression of high-n Rydberg states in a tiny energy region below the ionization potential. Finally, fluorescence depletion data of NO trapped in amorphous sites (the so-called red sites) of solid Ar can be interpreted in terms of the gas phase NO-Ar van der Waals data. A general discussion on the fate of Rydberg states in van der Waals complexes, in liqs., and in solids is presented in an attempt to relate the data in these different media. [on SciFinder (R)]